[#137] Refactor context data retrievers

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

api/middleware/util.go

@@ -0,0 +1,72 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/creds/accessbox"
+)
+
+// keyWrapper is wrapper for context keys.
+type keyWrapper string
+
+// authHeaders is a wrapper for authentication headers of a request.
+var authHeadersKey = keyWrapper("__context_auth_headers_key")
+
+// boxData is an ID used to store accessbox.Box in a context.
+var boxDataKey = keyWrapper("__context_box_key")
+
+// clientTime is an ID used to store client time.Time in a context.
+var clientTimeKey = keyWrapper("__context_client_time")
+
+// GetBoxData  extracts accessbox.Box from context.
+func GetBoxData(ctx context.Context) (*accessbox.Box, error) {
+	var box *accessbox.Box
+	data, ok := ctx.Value(boxDataKey).(*accessbox.Box)
+	if !ok || data == nil {
+		return nil, fmt.Errorf("couldn't get box data from context")
+	}
+
+	box = data
+	if box.Gate == nil {
+		box.Gate = &accessbox.GateData{}
+	}
+	return box, nil
+}
+
+// GetAuthHeaders extracts auth.AuthHeader from context.
+func GetAuthHeaders(ctx context.Context) (*auth.AuthHeader, error) {
+	authHeaders, ok := ctx.Value(authHeadersKey).(*auth.AuthHeader)
+	if !ok {
+		return nil, fmt.Errorf("couldn't get auth headers from context")
+	}
+
+	return authHeaders, nil
+}
+
+// GetClientTime extracts time.Time from context.
+func GetClientTime(ctx context.Context) (time.Time, error) {
+	clientTime, ok := ctx.Value(clientTimeKey).(time.Time)
+	if !ok {
+		return time.Time{}, fmt.Errorf("couldn't get client time from context")
+	}
+
+	return clientTime, nil
+}
+
+// SetBoxData sets accessbox.Box in the context.
+func SetBoxData(ctx context.Context, box *accessbox.Box) context.Context {
+	return context.WithValue(ctx, boxDataKey, box)
+}
+
+// SetAuthHeaders sets auth.AuthHeader in the context.
+func SetAuthHeaders(ctx context.Context, header *auth.AuthHeader) context.Context {
+	return context.WithValue(ctx, authHeadersKey, header)
+}
+
+// SetClientTime sets time.Time in the context.
+func SetClientTime(ctx context.Context, newTime time.Time) context.Context {
+	return context.WithValue(ctx, clientTimeKey, newTime)
+}